Pitot tube flow sensors were invented based on the Pitot tube theory discovered by French scientist Henri Pitot. Pressure sampling head is the pressure sampling portion of a Pitot tube flow sensor.
A Pitot tube flow sensor includes a hollow cylindrical body, and the hollow cylindrical body contains an outer tube and an inner tube. The outer tube is connected to a total pressure channel and the inner tube is connected to a static pressure channel. A pressure sampling head is connected to the lower end of the hollow cylindrical tube. The pressure sampling head includes a cylindrical pressure sampling body. A cylindrical upper connecting portion is formed on the upper end of the cylindrical pressure sampling body. The cylindrical pressure sampling body of the pressure sampling head includes a total pressure channel and a static pressure channel, each of which has an axis parallel to the axis of the cylindrical pressure sampling body. The total pressure channel and the static pressure channel pass through the cylindrical upper connecting portion and form a total pressure channel opening and a static pressure channel opening on the cylindrical upper connecting portion. A total pressure sensing hole is formed on the lower end of the cylindrical pressure sampling body and is connected to the total pressure channel. A static pressure sensing hole is formed on the lower end of the cylindrical pressure sampling body and is connected to the static pressure channel. The pressure sampling head may be welded to the lower end of the cylindrical pressure sampling body. A Pitot tube flow sensor is made by connecting the pressure sampling head and the cylindrical pressure sampling body, connecting the total pressure channel opening to the outer tube, and connecting the static pressure channel opening to the inner tube.
When in use, a Pitot tube flow sensor, a pressure differential measuring device, and a flow totalizer are mounted together to form a Pitot tube flowmeter. The Pitot tube flow sensor is inserted into a pipe or conduit transversely through a side wall of the pipe or conduit. Total pressure sensing holes on the Pitot tube flow sensor face the upstream of the fluid flow and static pressure sensing holes on the Pitot tube flow sensor face the downstream of the fluid flow. When the fluid is flowing in the pipe or conduit, the total pressure data and the static pressure data of the fluid flow are output to the pressure differential measuring device through the total pressure channel opening and the static pressure channel opening, respectively. The pressure differential measuring device then transmits the differential pressure between the total pressure and the static pressure to a flow totalizer. The flow totalizer then calculates volume flow rate of the fluid flow based on the data and a Bernoulli equation.
In a Pitot tube flow sensor, the pressure sampling head connected to the lower end of the hollow cylindrical body has a big impact on precision of the pitot tube flow sensor. When a Pitot tube flow sensor equipped with the conventional pressure sampling head is used for measuring the volume flow rate of a pipe or conduit, because of the low precision of the conventional pressure sampling head, the final data obtained from the Pitot tube flow sensor is not precise enough. When a Pitot tube flowmeter consisting of a Pitot tube flow sensor containing a conventional pressure sampling head, a pressure differential measuring device, and a flow totalizer is used for measuring the volume flow rate of a pipe or conduit, the measurement precision class can only reach between 0.5-1.0.